It is known to treat molten metal with additives in the mold. Published German Application 19 36 153 discloses a process for making cast iron which contains nodular graphite that has been added in the mold. The apparatus used in that known process comprises a horizontally extending runner, which is followed by a downwardly offset, rectangular chamber, which contains spaced apart, vertical partitions, which define a passage. The partitions ensure that the cast iron entering the chamber will thoroughly be mixed with the inoculant so that a large contact surface between the cast iron and the inoculant will be obtained.
French Pat. 2,034,907 discloses a process and an apparatus for treating molten metal. The apparatus comprises a vertical downsprue and a following one-piece runner, which communicates with a reaction chamber, which enlarges the cross section of the runner and contains the inoculant.
The apparatus which is known from German Patent Specification 24 10 109 and serves to make nodular cast iron comprises a downsprue, which is succeeded by a horizontal runner. The inoculant is contained in a shallow recess, which is formed in the bottom of the runner and does not interrupt the laminar flow.
Published German Application 19 01 366 discloses an apparatus for inoculating, alloying or treating molten metal to be cast. The sprue for receiving the molten metal and/or cavity to be filled by the molten material is provided with a body which is adapted to be dissolved by the molten material and contains a granular inoculant and/or/alloying elements. That body may be made from polystyrene foam, which has been enriched with inoculant.
Another process of inoculating cast iron is known from German Patent Publication 12 48 239 and comprises contacting molten cast iron flowing through the sprue or gate system with an inoculant which has been embedded in said system. The inoculant may consist of a shaped body or a tubular member. The known processes and apparatuses have not produced satisfactory results in all cases. The shaped bodies may not present sufficiently large surfaces to the inflowing melt for a dissolving action or undesired turbulence may be generated or undissolved particles of the treating agent may be detached and will then constitute inclusions in the casting or the economy may be low because an excessive quantity of undissolved treating agent remains in the sprue system of the mold.